A magnetic memory cell or device stores information by changing electrical resistance of a magnetic tunnel junction (MTJ) element. The MTJ element typically includes a thin insulating tunnel barrier layer sandwiched between a magnetically fixed layer and a magnetically free layer, forming a magnetic tunnel junction. The magnetization of the free layer can switch between first and second magnetization directions while the magnetization direction of the fixed layer is fixed in the first magnetization direction.
A fixed layer typically includes a hard layer and a reference layer separated by a spacer layer. The hard layer is used to pin the magnetization direction of the reference layer. It is important that the MTJ element has high tunnel magnetoresistance (TMR) and can sustain high processing temperatures, such as those employed in back-end-of-line (BEOL) complementary metal oxide semiconductor (CMOS) processing. However, conventional MTJ element tends to have TMR degradation when exposed to high temperatures.
In view of the foregoing, it is desirable to provide a MTJ element with improved TMR and enhanced thermal endurance and thermal budget. Furthermore, it is also desirable to provide a process for forming such MTJ elements which is cost effective and compatible with CMOS processing.